Apparatus for welding seams



Feb. 5, 1946. H. T. ODQUiST APPARATUS FOR WELDING SEAMS Original FiledJuly 1, 1939 5 Sheets-Sheet l [III/II/II/ 11 IIIIIIIIIIII 1/1 [l Q;[III/111111 INVENTOR M J a: BY 3 A? 1% Original Filed July 1, 1939 5Sheets-Sheet 2 INVENTOR. 7

Feb. 5, 1946. I H. 'r. ODQUIST 2,394,004

APPARATUS FOR WELDING SEAMS Original Filed July 1, 1939 5 Sheets-Sheet 3INVENTOR.

M Z BY 94m. 62

N ATTORNEYS Feb. 5, 1946. H. T. ODQUIST APPARATUS FOR WELDING SEAMSOriginal FiledJu ly l, 1939 5 Sheets-Sheet 4 INVENTOR.

AT ORNEYS Feb. 5, 1946. H. r. ODQUIST 2,394,004

APPARATUS FOR WELDING SEAMS Original Filed July 1, 1939 5 Sheets-Sheet 5ATTORNEYS Patented Feb. 5, 1946 UNITED STATES PATENT OFFICE 2,394,004arrmrus roa wammo scams Harold 'r. Odquist, Yonkers, N. Y., assignor toAmerican Can Company, New York, N. Y., a

corporation of New Jersey Original application July 1, 1939, Serial No.282,553, now Patent No. 2,323,349, dated July 6, 1943. Divided and thisapplication October 27. 1942, Serial No. 463,527

2 Claims.

The welding of a side seam of a metallic can body which consists of aplain lap section, an

- ofiset lap section and a lock section may be considered asexemplification of work requiring varied welding treatment. Certaintypes of can bodies require a smooth even surface throughout the insideas where critical interior coating is necessary. An offset lap weldedside seam presents the best interior surface for this purpose.

A small section of a welded lock seam of such a can may be desirable toassist in holding the can wall during welding, as this will insureuniiormity in can diameter, A plain welded lap seam at an end of theside seam is better than the offset lap structure where such an endsection is to be enclosed in a double seam as in the connection betweenthe can body and an end member (such as a top or a bottom). Each ofthese difierent seam sections requires a diflerent welding heat toproduce a proper weld. a

If a welding heat is supplied to the entire seam that is sufllcient toweld the lock seam section, the ofiset lap section and also the plainlap section will receive too much heat and these parts will be burned.It a proper welding heat is supplied to weld the ofiset section, thelock seam portion will not be welded sufliciently and again the plainlap section will be burned. Obviously the application of welding powerand heat which is proper for performing a weld of the plain lap sectionwill leave the oflset lap and the lock seam region unwelded.

Beside burning seam sections, where too great a welding heat is appliedto the seam, such excessive heat has a destructive eiiect on theelectrodes used, thereby resulting in a rapid deterioration of thesemembers as well as causing other damage to the machine. On the otherhand where the side seam of the can body is not properly welded, theresulting can will leak and be unsatisfactory as a container for certainproducts.

The present invention contemplates an apparatus for welding wherein adifferent welding energy is supplied to the diflerent kinds oi seamsections, such power being automatically delivered in predeterminedamount in accordance with the predetermined requirements at anyparticular part of the seam being welded. This welding energy is undercontrol of an electronic panel in which space discharge devices such asthyratron or ignition tubes are ionized by improved external means toeffect properly timed conductivity of the tubes as required.

An object of the invention is the provision of I an apparatus forwelding sheet material by delivering welding energy to electrodes by anelectronic control panel utilizing space discharge devices andelectrically and mechanically eflecting conductivity of the tubes inpredetermined relation to the requirements of the section being weldedso that the desired degree of welding heat is imparted to the work.

Another object of the invention is the provision of such a weldingapparatus wherein the welding power delivered to the electrodes isadjustable, as to both quantity and timing, so that a particular weldingoperation is automatically obtained on work which by its nature requiresa different welding treatment throughout diflerent sections.

Still another object is the provision of a welding apparatus which isadapted to welding relatively thin metallic sheet material which variesin welding resistance throughout the part to be welded, the weldingpower being at all times under direct action of an electronic panel inwhich ionization of space discharge tubes, to render them conducting, ismechanically and electrically. controlled inrelation to the position ofthe electrodes on the sheet material being welded.

Yet another object is the provision of an apparatus capable of supplyingthe proper mechanical actions for delivering the proper amount ofwelding energy to the electrodes in accordance with the character of theseam sections passing into the zone of action of such electrodes.

Numerous other objects and advantages of the invention will be apparentas it is better understood from the following description, which, takenin connection with the accompanying drawings, discloses a preferredembodiment thereof.

Referring to the drawings: Figure l is a perspective view of a can bodyhaving a side seam formed of sections requiring different weldingconditions and illustrating work adapted to be welded in the apparatusof the present invention;

Figs. 2, 3 and 4 are cross sections taken through the side seam alongthe respective section lines 2-2, 3--3 and 4-4 in Fig. 1;

Fig. 5 is a sectional view of some of the principal parts of a weldingapparatus for performing a welding operation on a can body in accordancewith the present invention, parts being broken away;

Fig. 6 is a plan sectional view taken substantially along the brokenline 6-6 in Fig. 5;

Fig. '7 is a fragmentary detail taken along the line l'| in Fig. 5;

Fig. 8 is a sectional view on an enlarged scale showing one of themechanical timing switches as taken substantially along the line 8-8 inFig. 5;

Figs. 9 and 10 are similar views of another of the switches as takenalong the section lines 9-9 and |ll|l in Fig. 6 and on an enlargedscale;

Fig. 11 is a wiring diagram of the electrical circuits used in theapparatus; and

Figs. 12 and 13 are diagrammatic views showing curves of various Weldingphases of the invention.

The present invention is directed to apparatus for welding by the use ofcertain improved switch and other electrical controls associated withthe proper Wiring and welding circuits utilizing space discharge tubesrendered conducting at predetermined time intervals to perform desiredwelding operations asrequiredby the work. i. e., the parts being welded.As such a manner of welding is quite flexible under varying weldingconditions, a type of work is selected which shows varied weldingrequirements and such a Work will first be considered.

Fig. 1 illustrates a tubular can body a circular in cross section andhavinga side seam b. This side seam is formed with a lock section atabout its center which is produced by two distinct hooks d, e (Fig. 4)interengaged and pressed tightly together. Such a lock section of theside seam requires a considerable amount of welding energy to produce aweld.

At each end of the side seam b there is a plain lap section 1 (Fig. 2)wherein one edge of the body is lapped over the other edge. Such a plainlap section requires the minimum of welding energy. The seam b in othersections is lapped but in addition is offset which means that in thesesections one part of the lap instead of being straight is bent to forman oifset edge g (Fig. 3). These sections require less welding energythan the lock section c but more than the plain 1ap sections J.

It will be observed that on the inside wall of the sections 0 and g themeeting parts of the side seam are flush and this is the bestconstruction when a coated inner lining is desirable for the can.

The principal parts of an apparatus embodying the invention are shown inFigs. to 10, inclusive. The various machine parts are carried on a base2|. The can body a to be welded is placed upon a horizontally disposedhorn 22 (Fig. 5) in any suitable manner with the edges of the body,which are to form the side seam b, beneath the horn. An insert bar 23 isdisposed in the horn and provides an inner, stationary electrode. Thispart 23 extends for the full length of the seam and slightly beyond theends of the seam.

When the body ,a is placed on the horn 22 it is firmly held in propercylindrical or other shape against the outer surface of the horn by sidewings 25. These may be hun from a pivot stud 26 projected out from theface of an upper frame 21. It will be understood that the bending of theblank into body form m y be done by rollers. forming wings or bysuitable forming or shaping mechanism common in can body makingmachines.

Actuation of the wings 25 may be imparted through the medium of links 28pivotally connected to the wings and operable to clamp and hold theparts 0, f and g of the side seam b when in proper position for welding.

A movable electrode may be caused to traverse the side beam b from oneend to the other, such electrode engaging below the lapped and hookedparts of the seam during which time suitable welding energy passesbetween the movable electrode and the fixed electrode 23 in the horn andthrough the side seam part therebetween.

Such a movable electrode is preferably a roller disc 3| mounted on ahorizontal shaft 32. Shaft 32 is journaled in bearings 33 formed onbracket extensions 34 of a slide 35. This slide has longitudinalmovement alongside and beneath the horn 22 but is insulated from theframe of the machine. It is retained in slideways 36 formed in a table31. Slide gibs 38 are bolted to the table and these hold the slide 35 inits slideways 36. The table 31 may be a part of a frame 39 mounted onthe base 2|. A bracket 4| also mounted on the base 2| is shown in thedrawings as supporting one side of the table.

The slide 35 is moved back and forth so that the roller electrode 3|traverses the seam to perform the welding. Suitable Provision may bemade for lowering the electrode 3! from its position relative to thehorn 22 to more readily allow for positioning and removing of the canbodies before and after welding. This is a constructional detail whichmay assume various mechanical forms not of particular pertinence in thepresent disclosure.

As illustrated in Fig. 5 slide 35 is formed with depending lugs 45 whichare adapted to more through a slot 45 cut in the table 31. These lugs 45(see also Figs. 6 and 7) are pivotally connected at 41 to a link 48, theother end oi which is pivotally connected at 45 to a vertically disposedrocker arm 5|. The arm 5| is pivotally mounted at its lower end on a pin52 which is carried in lugs 53 formed integrally with and projectingupwardly from the base 2 l,

The bodily sliding movement of the lower electrode 3| through theconnection now being considered is efiected by cam action and for thispurpose there is provided a cam 55 which is cai ried on a horizontallydisposed drive shaft 58 journaled in a bearing 51 formed in the framewall 39 and in a bearing 58 formed in the bracket 4|. A cam groove 59(Fig. 7) cut in one face of the cam 55 provides actuation for a camroller 6| mounted on a pin 82 disposed intermediately of the lever 5|.As the cam 55 turns with the rotation of the shaft 56, the cam groove 59controls the rocking movement of the lever 5| and, through the describedconnections, this produces a controlled reciprocating back and forthmovement of the slide 35 and the lower roller electrode 3|.

Drive shaft 56 is driven by a synchronous motor which insures constantand correct timing of the movements of the electrode and controlswitches with the welding current impulses. Shaft 56 carries a bevelgear 65 which meshes with a bevel pinion 56 carried on a horizontallydisposed intermediate shaft 51. The shaft 61 is journaled in bearings 68(Fig. 6) formed on The moving electrode 3i may be eflective for weldingduring the forward stroke and after the welding is completed may bereturned along its path of travel without doing any work or may weld inboth-directions. The exact timing of the welding current as it-isdelivered to the two electrodes 23, 3i and the exact amount of weldingenergy at any particular time in the welding cycle are under fullcontrol and will be more thoroughly discussed in connection with aconsideration of the welding circuits shown in Fig. 11.

It might be said at this time that the electrical current is completedto the moving electrode 3| through a collector bar 8| (Fig. 5) which ismounted upon a bus bar 82 in turn carried on and insulated from anintermediate bracket 83. This bracket is supported from the frame 38through the medium of a lower bracket 88. The bar 8| is stationary butelectrical contact is made at all times between the lower electrode 3|and the bar irrespective of the position of the lower electrode relativeto the seam being welded. The electrode shaft 32 at one side carries aspring pressed sliding disc 88 which engages against the inner face ofthe collector bar 8I and completes the circuit between the fixed frameparts and the moving electrode.

In high speed welding it is desirable to keep the electrodes cool toprevent overheating under constant repeated welding conditions and acooling medium may be circulated through parts of the electrode andthrough parts of the bus bar details of two diflerent switch deviceswhich are used for this purpose.

The switch device illustrated in Fig. 8 and designated broadly by thenumeral 84 is a double pole switch, 1. e., two different circuits aresimultaneously affected. 'This switch unit is contained within a housing88 secured to one side of the frame 38 (see also Figs. 5 and 6). Theactuate ing' parts of this switch unit are carried on the drive shaft88, being mounted on a sleeve 88 which is keyed to the shaft. Adjacentthe frame wall 38 the sleeve 88 is enlarged in a flanged head 81.

Four cam rings 88 are loosely mounted on the a sleeve, alongside oneanother, and these rings maybe independently adjusted as to position onthe sleeve. Each ring has a peripheral projecting cam surface 88 whichfunctions as a switch actuator and it is the proper positioning of thisprojecting part that determines the timing of the switch unit in thewelding cycle.

Each cam ring 88 is cut through in four arcuate slots MI and bolts I82passing throughthe slots are threaded in the flange head 81 of thesleeve. When the desired adjustment is made the bolts are clamped tightand the four cam rings are locked as a unit to the sleeve 88 andthereupon turn with the shaft 88.

The two inside cam rings work together as a switch actuator foreffecting welding of one can body and the two outside cam rings alsocooperate for the next following can body. In other words, the camsurfaces 88, either of the two inside cam rings or of the two outsiderings when set, provide a larger diameter periphery 88 for the pairwhich opens the contacts at a certain time in the rotation of the driveshaft 88 for the beginning of a weld, which maintains the contacts openuntil the full seam has been welded and which terminates welding byclosing the con-- tacts at a certain time.

to effect such cooling. This is a detail which is only incidental to thepresent invention but such a cooling system is suggested by pipes 81threaded into a housing 88 which encloses one end of the electrode shaft32. A cooling medium such as cold water may be circulated through thehousing and the heat of the electrode will be dispersed to suflicientextent by such cooling arrangement. Pipes 88, carried in the bracket 82and leading into the bus bar 8|, may be used as part of the circulatorycooling system in the same manner,

The details of the welding horn 22 are not embodied in the presentdisclosure as such a horn may take on a variety of shapes andconstructions. make the horn collapsible so that after a body a has beenwelded it may be more easily slid oif the horn. Slide bars 8i areillustrated in Fig. 5 and are shown as being transversely mounted in theholding jaws or side wing members 28 to suggest this removal of a weldedcan body from th horn. Such bars may also be used to feed the open canbody into welding position.

In carrying out a complete welding cycle according to the presentinvention it is necessary to vary the input to the welding transformerwhich supplies the welding energy in accordance with the requirements ofthe several sections of the seam, mechanisms for this purpose taking theform of mechanical switches by means of which the constants of thecontrol circuit may be changed. Fig. 8 and Figs. 9 and 10 illustrate Inmost cases it will be desirable to It will now be evident that there aretwo circuit openings and two circuit closing actions for the switch unitduring one'revolution of the drive shaft 88. In other words, only onehalf of a revolution of the drive shaft is used for one can body and thewelding of two can bodies takes place during one entire shaftrevolution.

A switch lever I88 is pivotally mounted at I88 on the housing 88. Onearm of lever I85 terminates in a widened rounded cam section I81. Thissection extends across the four cam rings 88 and therefore rides uponthe peripheral surface of one or more of the rings, either on the camprojections 88 or on the reducedperipheral surface of the four ring camswhich are the same diameter in their reduced non-projected sections.

The switch lever I85 at all times engages an insulated block IIIfastened to an arm II2 which is pivotally mounted on an insulatedbushing surrounding a pin II8 anchored in the housing 85. Arm I i2 isurged in a counter-clockwise direction by a curved leaf spring .I I8,the opposite end of which is secured to an insulating block H8 fixed onthe housing. The free end of the arm I I2 carries a'contact II8 which,when the switch lever I88 is in circuit closing position, rests on acontact pin II'I. Fig. 8, however, shows the'contact elements separatedand this part of the switch open.

electrical circuits which will be more fully described in connectionwith the wiring diagram. This part of the switch will be designated bythe letter in the later description.

The switch lever I65 is formed with a tail extension I2 I, the end ofwhich at all times rests against an insulated block I22 fastened to anarm I23. Arm I23 is pivoted on a Pin I24 secured in the housing 35. Thefree end of the arm I23 carries a contact I25 which, when the switchlever I35 is in circuit closing position, engages a contact pin I26.Fig. 8 shows these contact elements also separated. Pin I26 is anchoredin an insulated sleeve which is carried in the housing 35.

A curved leaf spring I23 connects with the arm I23 and urges the arm ina clockwise direction. This spring, when the parts are in circuitclosing position, holds the contact I25 and the pin I26 in contact. Thespring I26 is mounted on a pin I29 carried in an insulated sleeve whichis secured in the housing. The pin I26 is connected at alltimes with awire I33 and a wire "I connects with the pin I23 and the spring I26.These two wires form a part of a second circuit to be described later inwhich this part of the switch will be designated by the letter 2:.

It will be understood that the switches w and :1: are simultaneouslyclosed. They are also simultaneously opened when one of the projections33 of a cam ring passes into engagement with the part I01 of the switchlever I05, as shown in Fig. 8. Such engagement rock the switch leverclockwise simultaneously lifting the arm H2 and lowering the arm I23 andseparating the contact elements involved. Welding takes place when thesetwo switches to and :c are open, as will be fully explained hereinafter.

The switch devices shown in Figs. 9 and 10 are of substantially the sameconstruction and the operation in each case is the same. Each switch hasa single make-and-break action, Fig. 9 illustrating a switch which isreferred to by the letter 11 and the switch of Fig. 10 is designated bythe letter 2. Both switches are mounted upon the intermediate shaft 61(Fig. 6) alongside one another. Each is enclosed in a switch casing I32mounted on the base 2I (see also Fig. 5). The two may be tied togetherby bolts I33.

The shaft 61 is faster running than the switch actuating drive shaft 56.The entire cycle of welding for each can body takes place during asingle revolution of the shaft 61. Each switch :u and z is independentlyadjustable as to timing so that in each switch an electric circuit isestablished at the desired time by closing of contacts within theswitch. Such contacts remain closed for the desired time period,following which the contacts are separated and th corresponding circuitis broken.

The single circuit for each switch is a shunt circuit which controls, incooperation with the other switch circuit, the amount of welding en ergydelivered to the electrodes so that when minimum, intermediate ormaximum welding, heat is required by the nature of the work, suchrequirements will be met. It will be understood that additional switchesof this type may be used if there are more than three intensities ofweldare substantially the same construction. Each switch is permanentlyconnected to a wire at a contact pin I35. In the switch ll (Fig. 9) thiswire is designated by the numeral I36, while a wire I31 (Fig. 10) joinsthe contact pin I35 in the switch 2. The contact pin I35 of each switchis anchored in an insulated sleeve I38 which is secured in the casingI32.

A switch arm I33 (Figs. 9 and 10) is pivotally mounted on an insulatedsleeve carried on a pin I40 secured in the housing. The switch arm ofeach switch is connected with a curved leaf spring I4l which urges thearm in a clockwise direction. For this purpose, the opposite end of thespring is mounted on an insulated sleeve which is secured on a pin I42in the housing. The pin I42 electrically connects the spring I with awire. In the switch 11 (Fig. 9) this wire is marked I43, while a wireI44 connects with the pin in the 2 switch of Fig. 10.

An electric connection is made between the wires I36 and I43 for theswitch 11 and between the wires I31 and I44 for the switch 2 when acontact pad I45, carried on its switch arm I39, is brought into contactwith the contact pin I35. The making and the breaking of each of thecircuits between the contact parts I35, I45 is effected by moving theswitch arm I33.

A switch lever I41 (Figs. 9 and 10) is used for such a DurDOse and whenthe lever moves the arm, the associated spring I in each switch housingI32 is flexed. Lever I41 is pivoted at I48 to the housing and anintermediate upper part engages an insulated block I43 which is fastenedto each switch arm I39. The switch spring I keeps the block against theswitch lever at all times.

The shifting of the switch leve I41 and through it the movement of thearm I33, is effected by cam action. When either switch 1/ or z,therefore, is closed through the respective circuits in volving thewires I36, I43 and the wires I31, I44, the cam action is applied againstthe switch lever I 41 and the lever moves the switch arm I39, its springI4I yielding to permit such a movement. The cam action will first beexplained.

Within the switch housing I32 of each of the switches 11 and z, a sleeveI53 is keyed on the shaft 61. This sleeve is formed at one end inanenlarged'flanged head I 54. Two cam rings I55 are mounted on the sleeveI53 one against the other and the adjacent ring rests against the sleevehead I54. Each cam ring has a peripheral projecting cam surface I56which functions as a switch actuator to close the switch.

Each cam ring I55 is adjustable as to timing position on the sleeve I53, th two projecting cam surfaces I56 forming a continuous surface. Inswitch 11 (Fig. 9) this surface is nearly in extent. 'In switch 2: (Fig.10) it is only a, few degrees long. The reason for this will be madeclear when the wiring and the circuit operations are explained.

When the rings I55 have been properly positioned they are lockedtogether and are also clamped to the sleeve flange I54 by bolts I51.Arcuate slots I58 cut in the rings permit the individual adjustment ofthe rings.

The switch lever I 41 is provided with a widened rounded section I53which extends across both of the cam rings I55. The switch spring I alsokeeps the switch lever projection I 53 down against the periphery of oneor both of the cam rings.

When the normal or lesser diameter of the rings is passing the switchlever, this lever for g the switch 1/, is down in the position of Fig.9.

The same position is shown in Fig. for the switch z. At such a time thepad I48 and the contact pin I88 are separated. Where this conditionprevails in switch 1 the circuit including the wires I38, I43 isbroken..

In switch 2 this condition means a break in its circuit including thewires I31, I44. As soon, however, as the cam ring projecting surface I88engages the switch lever I41, th latter is lifted, the contacts arebrought together and the circuit as to that particular switch is closed.Obviously the switch 1 is closed for a much longer time than the switch2. This difference is occasioned by the different length of the seamsections 1 and g as will be later explained.

Reference should now be had to the wiring diagram of Fig. 11 for aclearer understanding of the welding circuits and of the results of thefunctioning of the various switches in their special timing. All ofthese controlling elements in the primary of the welding circuit actsothat the secondary welding circuit containing the electrodes 23, 3| willdeliver welding energy which is proper for the work to be welded andwhich is effective only during the desired welding cycle.

In the wiring diagram of Fig. 11, the numeral I15 indicates the electricgenerator which supplies electrical energy as an alternating current toa welding transformer I18. The secondary winding of such a transformerextends as a wire I11 to the lower or movable electrode 3|. This broadstatement of electrical connection is suihcient for the present purpose.It will be recalled that. from a mechanical standpoint, variousconnecting mechanical units such as the bus bar 8| (as shown in Fig. 5),sliding disc 86 and other connecting elements are included in thiselectrical connection with the lower electrodes.

The other side of the welding transi'ormers secondary winding extends asa wire I18 to the upper or fixed electrode 23. The welding energy istherefore the usual transformed welding impulse which results, in timeand amount, from the electrical energy entering the primary winding ofthe transformer I18. It is to the more accurate control of the kind aswell as the timing of such energy that the present invention is in largepart directed.

Ignitron control tubes of the mercury pool type are used in this primarycircuit of the welding transformer I18. Such tubes may be of the typedisclosed in United States Patent 2,069,283, issued February 2, 1937, tothe Westinghouse Electric and Manufacturing Co. on Electric arc device.Two such control tubes I8I, I82 are used jointly as a switch tointerrupt the current between welds and as a control device to lower thepower supplied to thewelding transformer "6 during certain phases of thewelding cycle.

A wire I83 connects one side of generator H 5 with one side of theprimary winding of the transformer I18. A wire I84 connects the otherside of the generator with the cathode of the tube or ignitron I82. Awire I85 connected between the wire I84 and the anode (indicated by thenumeral I86) of ignitron I8I, gives a joint connection between tubes I8I I82. The anode of ignitron I82 (which is numbered I81) is joined by awire I88 to the other side of the primary winding of the transformer I18and a wire I88 connected between the wire I88 and the cathode ofignitron I8I, provides the other pabrzaof the joint connection betweenthe ignitron tu When the ignitrons I8l, I82 are caused to conduct,current flows through one or the other, depending upon which half of thevoltage cycle is flowing through the alternating current circuit and thetransformer. Such a primary current is thus transformed as a weldingcurrent effective for welding the side seam b of the can body a (2);)..the horn 22 by utilization of the electrodes The ignitrons are causedto conduct by creat ing currents between igniters I8I, I82 of therespective tubes I8I, I82 and mercury pools I83, I84 contained in thetubes. Such creating currents ionize mercury vapor at the surfaces ofthe pools, as is well known in this art, and negative ions and arcs areestablished. At a time when a mercury pool I83 or a pool I84 isnegative, the anode I88 or the anode I81 will be positive with respectthereto and hence such positive anode will attract the negative ions.

One or the other of th ignitrons I8I, I82 thus conduct for each halfcycle of supply voltage. The ignitron whose anode is sufficientlypositive at any instant thus constitutes the conducting tube at suchtime the other tube is held back during that half cycle since itsvoltage is reversed.

Firing tubes 28I and 282 are used for control of the igniters I8I, I82.An igniter may be given a potential with respect to its mercury pool ata time when the associated anode of the i nitron is positive, byimposing a potential of the same sense as the anode with respect to itscathode pool by means of the conduction of a firing tube. Such anoperation connects the igniter to the anode with only a slightresistance drop through the firing tube.

The firing tubes 28I, 282 are preferably of the hot cathode gridcontrolled thyratron mercury vapor type. A firing tube very similar inconstruction and operation is disclosed in United States Patent2,106,831, granted February 1, 1938, to Westinghouse Electric andManufacturing Company on Electric control system. The firing tubes 28Iand 282 will now be considered.

Firing tube 28I contains a heater element which is indicated in thedrawings as a closed circuit 283 and which for the sake of simplicity isshown as including a battery 284 which is indicative of an independentsource of power, In commercial practice the proper transformer with theconnecting wire would undoubtedly be used with the power line instead ofthe battery.

The heater element within the tube is preferably surrounded by a cathodemember 285 which may be connected to a wire 286. A plate anode 281 isalso provided and may be connected by a wire 288 with the generator wireI84. Such an anode 281 is preferablyshielded by a screen grid 288 wh chmay be joined by a wire 2| 8 to the wire 288.

The control grid member oi this firing tube is indicated by the numeral2| I and is disposed between the cathode and the plate anode. Such agrid may be connected to a wire 2, This construction of tube with itsscreen grid provides a high impedance grid to anode circuit so that onlismall grid currents will flow.

In like manner the firing tube 282 is constructed with heater, cathodeand. 'grid elements. Its heater element is indicated in Fig. 11 as aclosed circuit 2I3 which in this exemplary disclosure includes a battery2I4. Within the tube,

the heater element is surrounded by a cathode member 2|; which may beconnected to a wire 2l8.

A plate anode 2" is also provided and may be connected by a wire 2|!with the generator wire I84. Such an anode 2H i preferably shielded by ascreen grid 2| 3 which may be joined by a wire 220 to the wire 2li.' Thecontrol grid member of this firing tube is indicated by the numeral 22!and is disposed between the cathode and the plate anode. Such a grid' isconnected to a wire 222.

Proper operating conditions are effected in the firing tubes 20!, 202and also in the control tubes NH, I82 by the use of a peakingtransformer 225. Transformer 225 has two primary and two secondarywindings. It is constructed with a high reluctance magnetic path in thecore on which the secondary windings are placed.

Accordingly as the flux rises in the core due to the inductive effect ofprimary current, magnetic saturation of the core path passing throughthe secondaries is quickly reached and the result is a series of sharppeaked voltage waves occurring in the secondary circuits in definitephase relationship with the sine wave or approximate sine wave of thevoltage applied to the primaries. This will be discussed more in detailin the later consideration of the wave diagrams of Figs. 12 and 13.

Voltage in the secondary of a transformer is dependent upon rate ofchange of magnetic. flux in the core and the wavefront of the secondaryvoltage is very steep. In the present invention accurate control of thephase relation of this peaked wave to the anode voltage of the firingtubes 20!, 202 is had and firing of the tubes is accurately held to thedesired point in the anode voltage wave. This also will be furtherdiscussed in connection with the welding phase curves of Figs. 12 and13.

Peaking transformer 225 has ;one primary winding one end of whichterminates in a wire 226 and the other end join with the generator wireI84. The wire 226 connects with a wire 221, which in turn is connectedwith the generator wire I83.

The other primary winding of the transformer terminates at one end in awire 228 and the other end of this primary winding connects with thegenerator wire I84. The wire 22! joins a resistance coil 229.

The power factor of a circuit containing resistance and reactance isdependent upon the ratio of the former to the latter. A transformer islargely an inductive reactance hence the power factor of a circuitincluding such a transformer will be relatively low. However, the powerfactor of a pure resistance is unity so that by introducing a resistor,which is practically non-inductive, in series with the primary of atransformer, the overall power factor of the combination is greater.Thus the phase of current in the circuit relative to the voltage appliedacross the circuit may be changed by varying the value of the seriesresistance.

A change in the phase of the current in the primary of a transformerproduces a like change in the secondary voltage. It is this principle ofintroducing a resistor in the primary of the peaking transformer whichis utilized in the particular circuit illustrated in Fig. 11 and whichis now being described a exemplifying a vital principle of theinvention, that of shifting the phase 01 the sharply peaked voltagewaves induced in the peaking transformer 22!.

The coil 22. constitutes a phase shifting resister. The control switches11 and z are electrically associated with this coil and with each other.An end sliding contact element 23| Joins with the wire 221 and ismovable along the coil. Current flowing through the transformer primaryby way of the wire 223, the coil 22!, element 2il and wire 22! issubjected to the resistance in the intermediate length of the coil. Theamount of resistance is varied by the position of the contact elementand the portion of the coil used, this being true of all sliding contactresistance constructions.

This amount of resistance is further momentarily varied at will byclosing both or one of the switches 11 and z. This closing of a switchpartially shunts out the resistor. By having both switches closed stillanother different resistance is made effective. It more variations ofresistance is desired other switches may be added. The wire II of theswitch 11 connects with the wire 22'! at the end which Joins with thecontact element 2". The other switch wire I joins with an intermediatesliding contact element 232 also movable along the coil.

The wire I31 of the switch 2 joins the wire I" at its point of juncturewith the intermediate contact element 232 and the other switch wire I isconnected to another sliding contact element 223. The element 233 isalso movable along the coil 229. By this arrangement the desired amountof welding energy is made available at any particular time so thatvarious welding conditions in the work being operated on can be met bythe proper welding heat at the proper time.

Three diiferent welding conditions are herein given by way of examplebut obviously more or less can be handled as desired. The adjustment ofeach of the sliding contact elements 23!, 232 and 233 is made accordingto the requirements of the work being welded. The different weldingenergy needed in the welding of a side seam b of the can body a, in theexample given, will be briefly considered in connection with thissliding contact adjustment and with the functioning of the switches y,z.

The center part c of the side seam b requires the maximum welding energyand this figure will determine the positioning of the sliding contact23! in its relation to the coil of the resistance 229. When this maximumwelding energy is being used both switches 11 and z are open.

In other words, neither of these switches has any effect on the weldingoperation and the full amount of determined resistance will be thatoffered by the coil winding from the connection with the wire 228 to thecontact 23]. Obviously the thickness and the kind of metal of the blankwill be factors in this determination of the proper welding heat needed.

When the movable electrode is in contact with the offset lap section 0of the side seam b, the proper welding energy needed will be less thanthe maximum and a lesser length of resistance coil 229 will be used.Without changing the po sition of the sliding contact 23!, which remainsset as long as the same kind of blank is being welded, that part of thecoil length not needed will be taken out by short circuiting through theswitch y. To adjust for this amount therefore it is only necessary toproperly position the inbias is maintained on the grid of the firingtube termediate sliding contact 282 on the coil to obtain the desiredlesser welding heat.

The minimum welding requirements are for the plain lap sections I 01'the side seam b. This means that a lesser length oi resistance 228 isneeded and the sliding contact 288 is accordingly set relative to thecoil so that the needed lesser amount of resistance for the desiredwelding energy is obtained by further short circuiting the resistancelength. This is done by closing the switch z which now works with theclosed switch 1/ to short cut the resistance not needed. It will beobserved that this setting is done without changing the setting oieither of the sliding contacts 28! or 282.

From what has just been explained, it will now be evident by referringto both Figs. 1 and 11 that the welding of the side 'seam b from end toend is controlled by variation of the effective resistance length of thecoil 228 as follows. In the beginning of the weld with the plain lapsection 1', the effective resistance length is from the wire 228 to thecontact 238, both switches 11 and a being closed. The offset lap sectiona is welded with an effective length of the resistance 228 as thedistance from wire 228 to the intermediate contact 282, the switch 1/being closed. At the eilective length is from the wire 228 to thecontact 28!, both switches 11 and a being open. Continuing onto theoffset lap section the efiective resistance length is again from thewire 228 to the contact 282. Finally the exit and lap j for the seam ismade with the short distance of the resistance from the wire 228 to thecontact 233.

From the foregoing it will now be readily seen why the projecting camsurface !88 is long in switch y (Fig. 9) and relatively short in switcha (Fig. Switch 1 is closed while the two plain lap sections f and thetwo offset lap sections 9 are being traversed by the movable electrode,and will remain closed during positioning of a new body to be welded andduring removal of the body after welding. The switch a on the other handis closed during welding of the two lapped sections f of the seam b andwill also remain closed during positioning of a new body to be weldedand during removal of the body after welding. Obviously, this timing ofthe switches is a mat ter of adjustment as already fully explained.

The preceding reference to the peaking transformer 225 and to otherassociated elements has already dealt with the primary circuits of suchtransformer. The two secondaries of the peaking transformer will now befurther considered and the relationship between transformer secondarycircuits and the firing tubes 20! and 202 will be closely examined.

The grid-cathode circuits of the firing tubes 20!, 202 are fed by thesecondaries of the peaking transformer. Tube 20! is thus connected witha secondary winding 24! (Fig. 11) of the peaking transformer. ()ne endof the winding of secondary 24! is joined by a wire 242 to a battery243, the other side of the battery being connected to one end of thewire 208. The opposite end of wire 288 terminates at the igniter I 8! towhich it is connected and is also joined to cathode 205. this completingthe grid-cathode circuit.

The opposite end of the secondary winding 24! is connected to one sideof a resistor 244, the other side being connected by a wire 245 to theadjacent side of another resistor 248. The opposite side of resistor 248is joined to the grid wire 2I2. Normally a suitable negative directcurrent 20! by the battery 248. Obviously other current sources could beused but for the sake of simplicity such a battery arrangement isadequate 8 for the present desired results.

All grid biasing voltages for the firing tube 20! must flow through theresistor 248 and mayor may not flow through the resistor 244. Resistor248 therefore acts as a current limiting device and preventsdestructively high currents from flowing through the grid.

A capacitor 241 is interposed between wires 208 and H2 and acts toabsorb any transient voltage by shunting oi the grid-cathode circuit.Such transient voltage might be induced in the grid circuits .due totransients occurring in the anode-cathode circuit. This feature alsohelps maintain the grid at a predetermined potential with respect to itscathode.

Before proceeding further with a description of operation of welding, itis advisable to briefly note the parts associated with the firing tube v202. These parts correspond in every particular to cathode 2!8 thuscompleting the grid-cathode circuit.

The opposite end 0! the secondary winding 28! is connected to one sideof aresistor 284, the other side being connected by a wire 288 to theadjacent side of another resistor 288. The opposite side of resistor 288is joined to the grid wire 222. Normally a suitable negative directcurrent is maintained on the grid of the firing tube 202 by the battery283.

All grid biasing voltages for the firing tube 202 must flow through theresistor 288 and may or may not flow through the resistor 284. Theresistor 288 thus prevents destructively high currents from flowingthrough the grid.

A capacitor 281 is interposed betwen wires 2 and 222 and acts to absorbany transient voltages by shunting of the grid-cathode circuit. Thiscapacitor 28! operates in every way analo gous to the companioncapacitor 241' for the other firing tube and these various features neednot be again repeated. 7

As shown in Fig. 11, wire N9 of switch 10 is connected to that side ofthe peaking transformer secondary 24! which joins with the wire 242. Theswitch wire !20 also connects the switch with the wire 245. A shuntresistor 283 is interposed between the end of the secondary winding 24!and the wire H9.

In like manner the wire I30 of switch a: is connected to that side ofthe peaking transformer secondary 28! which joins with the wire 282. Theother switch wire !3! also connects the switch a: with the wire 258. Ashunt resistor 28? is interposed between the end of the secondarywinding 28! and the wire !30.

The series resistors 244, 284 and the shunt re sistors 283, 28'! act toreduce switching transient and resultant arcing when switches w and a:are opened or closed.

It will be obvious from the foregoing that by 75 virtue of theconnection between wire 208 and its associated cathode 205 of the firingtube 2II, that a grid cathode circuit has been established whichincludes the bias battery 243 and the peaking transformer secondary Iand the wires and other parts connected therewith. Under conditionswhere no weld is being made the bias battery 243 maintains the grid 2 ata potential sufllciently negative with respect to the cathode 205 toprevent an electron stream from cathode 203 reaching the anode plate201.

At such a time of no welding the switch w is closed and shunts out anyefifective voltage from the secondary 24 I. The grid-cathode circuitthen includes wires 242, H0, switch w, wires I20, 245, resistor 246,grid wire 2I2, the grid 2| I, cathode 205, wir203 and battery 243.

The same corresponding condition obtains as to firing tube 202, theswitch a: being closed as to such a circuit during a no-weldingoperation. when switches w and a: are opened the firing tubes will becaused to conduct each time the transformer windings secondary voltagewaves become sufficiently positive during the positive half cycle toovercome the negative voltage of the bias batteries and to raise thepotentials on the control grids to sufficiently positive values to allowa conducting path to be established between cathode and anode.

Consider now the circuit during welding for the firing tube 20!, atwhich time the switch w is opened. The grid cathode circuit is nowconstituted by secondary 24I, resistor 244, wire 245, resistor-246, gridwire 2I2, grid 2i I, cathode 205, wire 205, battery 243 and wire 242.The firing tube 201 now conducting current to the ignitron ISI for thepurpose of starting a weld, a conductin path is established between thecathode 205 and the plate anode 201. In this new circuit there is nowincluded wire I84, 208, plate anode 207 and cathode 205 of the firingtube 20I, wire 208, igniter ISI, the mercury cathode pool I93 of theignitron, wires I89, I88, primary of welding transformer I16, wire I83and the generator I15.

Since the peaking transformer is properly phased with respect to thetube I8I there will at this time be a positive potential appearing onthe anode I8li with respect to the cathode W3. This positive potentialbrought to the igniter l9! by the conducting of firing tube 20I producesa high potential gradient at the surface of the cathode mercury pool andestablishes therewith an are as described in the Westinghouse Patent2,069,283, supra.

The striking of this are produces a highly ionized condition within theignitron tube and the main are between anode and cathode is established.This tube now conduct power from the generator I15 to the primary of thewelding transformer I16, as previously described, for approximatelyone-half cycle.

The same firing conditions prevail as to firing tube 202 and theignitron I82. If switch a: is allowed to remain open at the end of theionizing condition just described for ignitron IBI, the-firing tube 202conducts and causes the ignitron tube I82 to conduct in the same way asthat of ignitron tube I8I. Thus it will be understood that as long asswitches w and 2: remain open, the ignitron tubes I8l, I82 conductalternately and the welding will thus proceed in accordance with thewelding energy delivered as determined by the switches :11 and 2.

It will be recalled that the statement was made above that a series ofsharp peaked voltage waves occur in the secondary circuits of thepeaking transformer 22!. There was also the further statement that suchpeaked waves bear a definite controllable phase relationship to the sinewave or approximate sine wave of the voltage on the primaries of thetransformer. This now will be examined in connection with Figs. 12 and13.

Control of the phase relation of the various circuits being anoutstanding feature of the present invention, the phase shifting for thedifferent kinds of welding will be graphically compared. In the exampleof work for welding given in the preceding description and shown in Fig.l as seam parts I, g and c, the welding energy required for the plainlap I is the minimum, that for the part g is next or an intermediateenergy and for the section 0 the maximum welding energy.

In the wave diagrams of Figs. 12 and 13 only two of these three weldingconditions are shown and it is believed that this is adequate for thepresent purposes since the actual curves and absolute phase shiftinangles are unimportant to the description. The comparison between or therelative values of a higher welding heat and a lower welding heat areimportant.

For this explanation it will be assumed therefore that Fig. 12 shows thevarious current behaviors when the seam part c is being welded, thisbeing for maximum welding heat in the example given. Fig. 13 can then beconsidered as graphically showing a lesser welding heat requirementwhich may be for either the seam parts I or g. It will be assumedarbitrarily therefore that the curves of Fig. 13 show the welding of theplain lap seam sections From this it follows that the intermediatewelding curves for the seam sections a, while not specifically shown,nevertheless come somewhere between the curve positions of Figs. 12 and13.

In both Figs. 12 and 13 the units of time are plotted as abscissa andunits of voltage and amperes are plotted as ordinates. The line A-A isthe zero or axis line. B designates the sine wave of the voltageappearing across anode to cathode of the firing tubes 2M 202.

Curve C is also a sine wave and is herein used to represent what wouldbe a current wave through the primary winding of the welding transformerI16 if all tubes were fired to correspond with the overall natural powerfactor of the entire welding circuit.- The distance marked D indicatesthe time lag or electrical phase angle corresponding to this naturalpower factor,

The horizontal lines marked E and F represent the negative bias normallymaintained on the control grids 2I I, 22I of the firing tubes 20I, 202by means of the batteries 243, 253. The E line is below the zero axisline A-A and represents a voltage applied to the tube capable ofconducting in the positive half cycle, Line F is above the zero axisline and represents the bias voltage associated with the other firingtube which is capable of firing during the negative half cycle.

On lines E and F there are shown the sharp peaks in the voltage wavesjust mentioned. These peaks on line E are lettered h, i, 7', in Fig. 12and k, l, m in Fig. 13 and represent peaked voltage produced by one ofthe peaking transformer secondaries I or 242. On line F the peaksproduced by the other of the transformer secondaries are lettered m ando in Fig. 12 and p in Fig. 13.

Only those peaks acting in the positive direcasocooa.

tion, suchas h. 1.1:, mm andpareofusein reducing the negative grid biasto or below the critical grid bias of the firing tubes 20!, 202. Such,critical grid bias is indicated by dotted curve linesG andHinbothFigs.12 and 13.

The critical grid bias represented by the lines G and H is derived fromthe characteristics of the individual tubes and will start at pointscorresponding to minimum arc establishing potential required for Zerobias with a particular tube. This is graphically shown in Fig. 12 as apoint q. when these critical grid biases are exceeded by thesuperimposed peaks, graphically shown as points 1- and s, the firingtubes "I, 202 will pass current. A few micro-seconds later, this currentpassing through the igniter IN or I92 of its corresponding ignitron tubeIII or I82, causes that tube to conduct.

When a voltage peak, h or n. for example, reduces the bias below thecritical value, as at a point r or s and the tubes flre, current willtend to start as at a point t in Fig. .12. Since magnetizing current forthe welding transformer has not previously been supplied, atransient'current occurs in the reverse direction tending to oppose thenormal direction of current flow. This is indicated by the sudden risefrom a point u to a point 12.

Such a. transient dies out logarithmically as I from the point v to apoint up and would eventually become zero,were it not for the firing ofthe opposite pair of tubes. The actual current conduction loop, letteredJ, is the algebraic sum of the natural conduction loop C and thetransient loop 12 to u The actual current does not continue beyond thezero value point, marked 11 in Fig. 12, even though the transient hasnot yet reached zero as the tubes are capable of conducting in only onedirection.

Comparing now Fig. 13 with Fig. 12 in which the corresponding curves arelocated in accordance with the diiferent welding heats used, it will beobserved that a distance K (Fig. 12) of the greater welding heat is lessthan a distance L (Fig. 13) of the lesser heat. This distance whichrepresents the phase shift between the axis beginning of the voltagesine wave B and the axis beginning of the current conduction loop J,graphically illustrates the eiiect of changing the resistance of thecoil 229 (Fig. 11) by closing the switches y and z. The phase of thesecondary voltage of the peaking transformer 225 in respect to the sinewave B is retarded when switches 11 and z are closed.

It now follows that the loops of the curve J in Fig. 13 graphicallyrepresentpulses of current through the welding transformer I16 underthis retardation of the control phase. The loops of the curve J of Fig.12, on the other hand, represent pulses of current through the weldingtransformer when the resistance coil 229 is operating at its maximumresistance for the maximum welding requirements of can body seam b nowbeing considered.

The areas, marked M in Fig. 12 and the corresponding areas, marked N inFig. 13, which is contained between the zero lines and the respectivesections of the curve J, are indicative of the relative amount ofwelding energy obtained by this control for the side seam section andthe side seam sections f. ()bviously, area N is smaller than area M.

From the foregoing it will now be evident that by the proper adjustmentsin the various switches w, a: and y, 2, which adjustments have beenfully provided for. and by the utilization of the various describedcircuits, that it is a simple matter to bring the peaks h, i, 1:, m, nand p, of the biasing curves E, F to positions where it is possible tocurred, the next peak will be shifted by that desired amount which wasestablished during the setting of the sliding contact elements 23l, 232or 233 for these switches. Such setting allows for adjustment of thegrid voltage peaks over a range of substantially 180 electrical degreesso that welding power pulses of from nearly zero value to maximum may beobtained.

It is thus possible to start welding at some predetermined power input,as for the seam section I, change to another power input, as for 9,change again for section 0 and change back again through the reverseorder, all within the time required to weld one piece of work. Suchpower change is timed in with the movement of the electrode 3i, allwithout detrimental disturbances in the welding circuit, producing thedesired conditions in the several sections of the welding seam.

It will be understood that even though a resistance type of phaseshifter has been illustrated in Fig. 11 and described herein, the claimsof the invention are not limited to this type of phase shifting circuitas there are other forms of phase shifting devices such as varied orvariable inductors and varied or variable capacitors, or these elementsin combination, or in combination with varied or variable resistors.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description, and it will beapparent that-various changes may be made in the form, construction andarrangement of the parts without departing from the spirit and scope ofthe invention or sacrificing all of its material advantages, the formhereinbefore described being merely a preferred embodiment thereof.

I claim:

1. In a welding apparatus for electrically welding metallic seams havingsectionsarranged in a given pattern and requiring diilerent weldingtreatments, the combination of an electrode for traversing the seamsections, means for maintaining relative movement between the seam andsaid electrode, an electrical welding circuit for energizing saidelectrode having conducting ignitron tubes and firing tubes and aphase-shifting circuit for effecting an uninterrupted heat input ofvariable magnitude during said relative seam and electrode movement,means comprising switch elements located in said welding circuit forvarying the magnitude of the heat input during the welding cycle bycontrolling the phase-shifting circuit of said welding. circuit, andmeans operated by said motion-maintaining means for actuating saidswitch elements to vary said heat input in a pattern corresponding withthe welding requirements of said seam sections.

2. In a welding apparatus for electrically welding metallic seams havingsections arranged in a given pattern and requiring different weldingtreatments, the combination of an electrode for traversing the seamsections, means for maintaining relative movement between the seam endsaid electrode, an electrical welding circuit for energizing saidelectrodes having conducting ignitron tubes and firing tube; and aphase-shitting circult for eiiecting an uninterrupted heat input ofvariable magnitude during said relative seem end electrode movement,means located in aid welding circuit for varying the magnitude oi theheat input during the welding cycle by controlling the phase-shiningcircuit of said welding circuit, nnd meme operated by saidmotion-maintaining menu (or actuating said maznitude varying meme tovary said heat input in a pattern corresponding with the weldingrequirements or said scum sections.

HAROLD '1. OD QUIBT.

